Piezoelectric devices are known to be useful as solid state actuators or electromechanical transducers which can produce mechanical motion or force in response to a driving electrical signal. Stacks of piezoelectric disks have been used, for example, to generate vibrations, i.e. acoustic waves, in pipes as a means of telemetering information. Such transducers are used in drilling operations to send information from downhole instruments to surface receivers. The downhole instruments generally produce an electrical waveform which drives the electromechanical transducer. The piezoceramic stack is typically mechanically coupled to a pipe or drill string by external shoulders. The transducer generates acoustic waves in a drill pipe which travel through the drill pipe and are received at another borehole location, for example at the surface or an intermediate repeater location. A receiver may include a transducer such as an accelerometer or another piezoelectric device mechanically coupled to the pipe. The received acoustic signals are converted back to electrical signals by the receiving transducer and decoded to recover the information produced by the downhole instruments.
Such piezoceramic materials have not typically been used for other downhole purposes due to their size, shape and brittle characteristics which make them incompatible with downhole structures. Most downhole structures are tubular. There are few flat surfaces for attaching piezoelectric materials. The shoulders required for mechanically coupling the conventional piezoceramic stacks extend from the outer surfaces of the tubular member, e.g. drill pipe, and occupy precious space or require use of larger bits or casing which increases drilling costs.
It would be desirable to provide other transducer structures and applications useful in downhole assemblies and other oilfield structures.